1. Field of the Invention
The present invention relates to a communication technology using both radio communication and the Internet, and, particularly, to a technique for monitoring the use conditions of a remote repeater.
2. Description of the Related Art
FIG. 11 is a structural diagram showing the outline of a D-STAR (Digital Smart Technologies for Amateur Radio) system which is one example of a communication system using both radio communication and the Internet.
This D-STAR system uses an IP (Internet Protocol) network (hereinafter referred to as Internet). The D-STAR system has a plurality of repeater stations 2 for each of a plurality of zones 7 to relay radio waves from a radio device or radio 1, and a gateway 3 which manages the operations of the repeater stations 2 and relays communication between the repeater stations 2 and an Internet 5. In each zone 7, all the repeater stations 2 are connected by a trunk line 4 which is a high-speed dedicated line. The Internet 5 is connected with a management server 6 which manages communication information or the like of the individual radios 1.
Each radio 1 has a user ID (e.g., call sign of the amateur radio) or a unique identification code to specify a user. Each repeater station 2 has an area ID (e.g., call sign of the amateur radio) or an address to specify the radio communication range. Each gateway 3 and the management server 6 are given IP addresses for specifying their positions on the
Internet.
In such a D-STAR system, each gateway 3 monitors the state of the radio 1 present in each area via the repeater station 2 in the same zone 7, and informs the management server 6 of the communication information or the like of each radio 1 via the Internet 5. The management server 6 saves the communication information or the like of the radio 1 informed by each gateway 3 in a database, and informs the communication information or the like of each radio 1 in response to an inquiry from each gateway 3.
In a case where, for example, a radio 1a in a zone 7a communicates with a radio 1b in a zone 7b in the D-STAR system, the sender radio 1a transmits, to a repeater station 2a, a message of voice, data or the like, by designating the user ID of the destination radio 1b. The message transmitted from the radio 1a is received by a repeater station 2a present in the area where the radio 1a is located, and is transferred to a gateway 3a directly or via the trunk line 4.
The gateway 3a informs the management server 6 of the user ID of the destination radio 1b, and inquires about the communication information or the like of the radio 1b. Then, the gateway 3a acquires the area ID of a repeater station 2b communicatable with the destination radio 1b and the IP address of a gateway 3b which controls the repeater station 2b from the management server 6. The gateway 3a adds the acquired IP address and area ID to the message transmitted from the radio 1 a, and transmits the resultant message onto the Internet 5.
Upon reception of the message, transmitted from the gateway 3a, via the Internet 5, the destination gateway 3b transfers the received message to the corresponding repeater station 2b according to the area ID added to the message. The repeater station 2b converts the message transferred from the gateway 3b to a radio signal, and transmits the radio signal to the radio 1b. This allows the radio 1b located in the area of the repeater station 2b to receive the message from the sender radio 1a. 
As apparent from the above, the D-STAR system uses the Internet 5 as a relay circuit to enable communication between remote radios 1 which cannot be covered by radio communication.
However, D-STAR system cannot know the status of a repeater station 2 provided at a remote site in an attempt to communicate with the repeater station 2. Problematically, this will cause a failure to connect to such a remote repeater station 2 when the repeater station 2 being busy, or will be the cause of interruption to the communication being performed by the repeater station 2.
As an art relating to this problem, Patent Document 1 (Unexamined Japanese Patent Application KOKAI Publication No. 2001-136206) describes a communication system which monitors what is talked over a transceiver and transmits the talking contents to a transceiver or the like located out of the communication range via the Internet. Patent Document 2 (Unexamined Japanese Patent Application KOKAI Publication No. 2002-330108) describes a radio communication monitor system in which radio transmitting/receiving devices that are sited zone by zone and perform transmission/reception communication with a plurality of radios are connected by an intranet, and the contents of communication between a radio transmitting/receiving device and a radio in another zone are monitored.
However, the Patent Documents 1 and 2 merely disclose techniques intended to monitor the contents of communication with another transceiver or the like, and have no description on monitoring the use conditions or the like of each repeater station which relays a message.